Highlight stray non-background pixelsIn Photoshop you could load the alpha channel of the layer as a selection and as long as the stray pixels are more than 50% opaque, they'd get highlighted by the selection marquee.

Nov14

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What program should I use for animated vector style graphics for an iOS gameIt's not clear from your question if you intend for the animations to be ultimately used inside the iOS app or if you're just trying to do mockups. If it's the latter I'm sure you'll find help on this board, if it's the former, gamedev will probably be able to better advise how to get the animations into the app. P.S. Illustrator used to do animation but I'm not an expert on that someone here will probably be able to advise though.